I think many of us will be getting both BoS and DCS WWII, I know I am. The good thing is they cover such a different part of war, that there is no overlapping and also now I don't have to wait for BoS to come to West or DCS going to East before getting to fly in that particular theatre.
About the planeset in DCS WWII, Spitfire mkXI is historically correct, it was used until the end of the war in most spitfire squadrons, if my memory serves right. Anyway allied planes will be good enough to hold their own against K-4 and D-9. That said, Tempest would be nice, and Fw 190 A-8 also. And Bf 109 G-10. And many others... Well, one can hope :)